﻿/*
 * Copyright (c) 2023 Proton AG
 *
 * This file is part of ProtonVPN.
 *
 * ProtonVPN is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * ProtonVPN is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with ProtonVPN.  If not, see <https://www.gnu.org/licenses/>.
 */

using System;
using System.Runtime.InteropServices;

namespace ProtonVPN.Common.OS.Net.Routing
{
    public static class PInvoke
    {
        private const string DllName = "iphlpapi.dll";

        [DllImport(DllName, CharSet = CharSet.Auto)]
        public static extern int CreateIpForwardEntry(IntPtr route);

        [DllImport(DllName, CharSet = CharSet.Auto)]
        public static extern int DeleteIpForwardEntry(IntPtr route);

        [DllImport(DllName, CharSet = CharSet.Auto)]
        public static extern int GetIpForwardTable(IntPtr pIpForwardTable, ref int pdwSize, bool bOrder);

        [DllImport(DllName)]
        public static extern int GetIpInterfaceEntry(ref MibIPInterfaceRow row);

        public static IPForwardTable ReadIPForwardTable(IntPtr tablePtr)
        {
            IPForwardTable result = (IPForwardTable)Marshal.PtrToStructure(tablePtr, typeof(IPForwardTable));
            MibIPForwardRow[] table = new MibIPForwardRow[result.Size];
            IntPtr p = new IntPtr(tablePtr.ToInt64() + Marshal.SizeOf(result.Size));
            for (int i = 0; i < result.Size; ++i)
            {
                table[i] = (MibIPForwardRow)Marshal.PtrToStructure(p, typeof(MibIPForwardRow));
                p = new IntPtr(p.ToInt64() + Marshal.SizeOf(typeof(MibIPForwardRow)));
            }
            result.Table = table;

            return result;
        }
    }
}